Cable ties are useful for quickly and securely retaining together two or more items, for example the conductors in a wiring harness. Several examples of cable ties are shown in U.S. Pat. Nos. 5,263,231; 5,440,786; and 5,615,455. In a general sense, a cable tie is an elongated tongue with a tip at one end and a locking head at the other end. A set of ratchet teeth are located on the underside of the tongue. The locking head has an integral movable pawl that is hinged at one side of an opening in the locking head. When the tip is inserted in the opening and pulled through the head, the pawl engages with the ratchet teeth to prevent the tip from being pulled back out of the opening.
When force is applied to an engaged cable tie, the tongue is pulled in a direction opposite to that in which it was inserted in the head. This causes the pawl to be pulled farther away from its attachment point, which pushes the tongue against the side of the opening opposite the pawl, termed the “abutment wall”. If sufficient force is applied, the abutment wall can bow outward, which can cause the ratchet teeth to release from the pawl.
One manner to alleviate this bowing is to increase the thickness of the abutment wall. However, the increased thickness requires an increase in the residence time of the product in the injection mold, so that the plastic cools sufficiently before the mold is opened to prevent shrinkage of the abutment wall. One proposed solution to this problem is disclosed in U.S. Pat. No. 5,615,455. The abutment wall includes a plurality of apertures extending within the abutment wall parallel to the direction of insertion of the tip in the head. The apertures are not exposed to the abutment surface. The apertures are elongated, and pairs of apertures extend along a common axis from opposite ends of the abutment wall, but do not join each other. This design is described as not requiring as much material as a similar thickness solid wall and so not being significantly subject to deformation when the injected plastic material cools.
However, this product would be extremely difficult to manufacture. In order to create the apertures in the abutment wall, the mold would have to have a series of very small pins that would be subject to deformation and breakage. In addition, much of the abutment wall is substantially thicker than the rest of the walls of the head. Accordingly, this design likely would not significantly decrease the amount of time that the product would need to be maintained in the mold to cool sufficiently before it is ejected from the mold so as not to cause bowing of the abutment wall.